How much roof overhang?

Discussion in 'Coop & Run - Design, Construction, & Maintenance' started by debid, Feb 1, 2011.

  1. debid

    debid Overrun With Chickens

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    I'm planning to put a simple slant roof on my coop. If I put a 12" wide ventilation hole running the full length of the coop at the top of the tall side, how much roof overhang would I need to keep the rain out? My husband thinks it's a crazy idea and we'd need 3' of overhang to keep the rain out if there was any wind at all. He's picked out some 2" wide aluminum venting strips that he wants to use on both the tall and short sides with the idea that the air will flow through this way and that will be more effective.

    Thoughts?
     
  2. Dogfish

    Dogfish Rube Goldberg incarnate

    Mar 17, 2010
    Western Washington
    If this is on the back side, go with 6". It would take a heck of a wind to push much rain in there.
     
  3. patandchickens

    patandchickens Flock Mistress

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    If I put a 12" wide ventilation hole running the full length of the coop at the top of the tall side, how much roof overhang would I need to keep the rain out?

    Sorry, would need mroe information -- depends greatly on what the pitch of the roof is, how much space between top of roof decking and the vent, and your climate and which way the coop is facing.

    As a general answer, I would say: if you expect winds to be actually blowing towards that vent, no amount of shed-roof overhang will really keep out the precipitation. So either put the coop with its "back" to yer problem winds, or in a sheltered enough location (in warm climate) that it doesn't really matter a lot, or think about putting a drop section or little 'porch roof' on the edge there to provide a more-useful overhang. Or, put vents in the opposite side too, so that on days when the wind blows from the front of the coop, you close those vents entirely and open the ones on the back wall.

    My husband thinks it's a crazy idea and we'd need 3' of overhang to keep the rain out if there was any wind at all. He's picked out some 2" wide aluminum venting strips that he wants to use on both the tall and short sides with the idea that the air will flow through this way and that will be more effective.

    As per above, if you are talking about wind blowing actually TOWARDS that side of the shed, he is essentially correct; however his idea will not work either, because it will result in *radically* insufficient ventilation [​IMG]

    Good luck, have fun,

    Pat​
     
  4. wyoDreamer

    wyoDreamer Chillin' With My Peeps

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    If by a single slant roof, you mean a roof that does not form a "/\\" but is a single "\\", it would depend on the slope of the roof if it would work or not. If you are putting a good slope on the roof to shed snow, then he may be right about the amount of overhang you would need. If the roof is almost flat, it may work OK.

    I believe that a 5:12 slope (5" up for each 12" over) on the roof is the least you would want for any snow. At a 5:12 you would need over 2' of over hang to stop a rain that is coming down at a 45 degree slant. Any decent breeze will blow rain at a greater angle than that.

    Having a narrow and long vent on each side of the coop will encourage air flow through the coop. A single vent on on wall - even if it is the entire length of the coop may not promote air to flow through the coop. For example, if I have all the windows on one side of my house open, there is almost no air flow through the house, but the minute I open a single window on the opposite side of the house, I get a gale blowing through.

    Just my thoughts, and I have been known to be wrong.
     
  5. darkmatter

    darkmatter Chillin' With My Peeps

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    Quote:See my BYC page for pics of my "slanted roof" Coop, it has been in use a couple decades now. I made the roof overhang about 12 inches all four sides. I also tarred each edge before I installed the metal drip edging. I also used aluminum under eaves ventilation panels. Every roof joint is over a joist and was caulked before I put tarpaper down, then shingles. I'm a fan of deep litter composting in a sub-ground dirt floor with the coop up on a solid rot-proof foundation. (I used brick, cause I had them free, excuse my bricklaying skills, I have none.)
     
  6. SandyK

    SandyK Chillin' With My Peeps

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    I think we put a 12" overhang on our side, maybe 24" on front. You can see pictures on my page.
     
  7. debid

    debid Overrun With Chickens

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    The pitch is 3:12 (12" of rise over 48" run). We don't get very much snow here (6" is a freak event, it's happened once in the 10 years I've lived here). We do get buckets of rain at times and severe storms in the spring and fall. The side I proposed venting heavily faces south. There is a building to the east and dense forest to the south and west. The side that gets the winter wind blast would be the short, long side where I've proposed hinged covers that are only opened in the summer heat.

    The other option would be to reuse the aluminum turbines we're taking off of the house. There are two of them at 14" each in good working order -- nothing wrong with them other than being 25 years old and ugly.
     
  8. elmo

    elmo Chillin' With My Peeps

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    You can also make awning style flaps for the vents which not only stop rain from blowing in but give you the ability to open or close the vents as needed. That's what I did on our last coop and it works beautifully.


    [​IMG]

    The roof overhang is 1 foot on all sides, and I have a vent just like the one pictured on the front of the coop as well.
     
  9. Bossroo

    Bossroo Chillin' With My Peeps

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    You can install the vents on the "bottom" side of the roof overhang and avoid the wind driven rainwater altogether !!!
     
  10. debid

    debid Overrun With Chickens

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    Quote:If I use 2x6 boards on end for the roof rafters, that makes a pretty big gap on two sides between the roof and the framing. How difficult would it be to cover the spaces created with hardware cloth? And, since the walls are 8' long, this would give me 8 sq. feet of "always open", rain-free ventilation from two sides. Then, on the other two walls with the slant, we could put in a couple of louvered vent panels as high up as they'll fit and get another sq. foot or two that way. Am I overlooking something or does this sound doable? We're putting 10 birds in here (if they all survive chickhood with a newbie!)
     

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